Real time brachytherapy spatial registration and visualization system

ABSTRACT

A method and apparatus for three-dimensional imaging and treatment of a patient&#39;s body. The method and apparatus utilize a system for developing a therapy plan for treatment of an organ of the patient, a device for generating ultrasound image data from a treatment region and a device for providing a translucent volume image of a portion of a patient&#39;s body and a separate translucent image of the patient organ and a three dimensional viewing device to superimpose a translucent article image to enable viewing of the article image simultaneously with the patient organ and a portion of the patient&#39;s body.

[0001] This invention is a continuation of U.S. application Ser. No.09/573,415 filed on May 18, 2000, which is a continuation-in-part ofU.S. application Ser. No. 08/977,362 filed on Nov. 24, 1997.

[0002] The present invention is directed in general to an improvedmethod and apparatus for carrying out minimally invasive treatments ofthe human body by virtual reality visualization of the treatment area.More particularly the invention is concerned with use of an apparatusand method for providing real time images of a human anatomy undergoingtreatment along with rapid radiation seed therapy planning and rapidperformance of therapy including an automatic seed loading methodologywhich enhances therapeutic treatment with greatly improved efficiencyboth in terms of time and resources.

[0003] New minimally invasive surgical procedures are most oftenoptically guided, but such optical guidance methods do not permitvisualization and guidance of instruments or probes within (inside) thetarget tissue or organ. Incorporation of real-time three-dimensionalvisualization inside diseased tissues would provide accurate guidance oftherapy. Open-magnet MRI is used to visualize some procedures such asthermal therapy and brain biopsies. However, the method is expensive,not truly real-time, and is limited in application.

[0004] Numerous conventional treatment methods involve attempts toprovide a targeted dosage of radiation or chemicals to the organ, andsuch treatments are often based on general anatomical assumptions ofsize and location. These methods suffer from inaccuracy of localizingthe target for any one particular individual and potential real timechanges of relative orientation and position of target tissue, normaltissue, and radiation therapy devices.

[0005] It is instructive in explaining the invention to consider onespecific type of exemplary condition, adenocarcinoma of the maleprostate which is the most commonly diagnosed cancer in the malepopulation of the United States. At present, 254,000 new cases ofprostate cancer were diagnosed in 1995 and 317,000 in 1996. In the1960s, a method of implanting radioactive gold or iodine seeds wasdeveloped. With this approach, the radioactive material is permanentlyplaced into the prostate via a retropubic approach during laparotomywhen diagnostic lymphadenectomy was also being performed. A high dose ofradiation is delivered to the prostate as the radioactive seeds decay.In several reports, the five year disease free survival (“localcontrol”) obtained by this method was compared to similarly stagedpatients treated with an external radiation beam. In view of this, goldwas replaced by I¹²⁵ implantation for safety of personnel doingimplantation. Except for early stage prostate cancer (T2a tumors),inferior rates of local control are reported with “free hand” 125-Iodineimplantation. There was significant dose inhomogeneity due to thenonuniformity of seed placement, leading to underdosing of portions ofthe prostate gland and significant complications due to overdosing ofadjacent healthy tissue structures. The poor results for local controland normal tissue complication were attributed to the doctor's inabilityto visualize and hence control where the radioactive seeds were actuallybeing deposited inside the patient.

[0006] Recently, transrectal ultrasonography (“TRUS”) has been used tovisualize 125-Iodine seed placement during transperineal implantation.The early reported rates of serious late complications is higher thanexternal beam therapy. Even with this technique, significantimprecisions in seed placement are observed. Due to the proximity of theprostate to the rectum and bladder, incorrect seed placement may lead toserious overdosing of these structures and late complications.

[0007] The recent transrectal ultrasound guided transperineal implanttechnique has been developed which is in use. That procedure isdescribed in three steps: (1) the initial volumetric assessment of theprostate gland performed using ultrasound, (2) development of aradiation therapy “pre-plan,” and (3) performing the actualintraoperative implant. The purpose of the initial volumetric assessmentprior to the pre-plan or implantation is to obtain a quantitativeunderstanding of the size of the prostate, which is then used todetermine the total activity and distribution of radioactivity which isto be implanted into the prostate. To perform the assessment, anultrasound probe is physically attached to a template. The template is aplastic rectangle which contains an array of holes separated atpredefined intervals, usually 5 mm. The template system serves twopurposes: (1) to fix the ultrasound probe, and hence the imaging planeto the reference frame of the catheter and seed positions, and (2) toguide the catheters into the prostate volume. More specifically, thetemplate system serves as a reference frame for spatial quantities whichare required for the description of the implant procedure. Usingtransrectal ultrasound, a number of serial ultrasound images areobtained at 5-mm intervals, and the prostate is outlined on each image.The images are taken so that the entire prostate gland is covered. Thisresults in a stack of two-dimensional outlines, or contours, which,taken together, outline the entire three-dimensional prostate volume.From this volume, the quantitative volume of the prostate is calculated.

[0008] Once the three-dimensional contour data has been obtained for theprostate volume, a radiation therapy plan which describes the positionsof the radioactive seeds within the prostate is developed. This planattempts to optimize the dose to the prostate, minimize the dose tosurrounding healthy tissue, and minimize dose inhomogeneity. Thepositions of the radioactive seeds are constrained to fall within thecatheter tracks, since the seeds are placed within the prostatetransperineally via these catheters. The result of the pre-plandescribes the positions and strengths of the radioactive seeds withinthe catheter which optimizes the dose to the prostate.

[0009] Intraoperatively, the TRUS probe is inserted, and the template ismounted against the perineum. As previously described, the template is aplastic rectangle which contains an array of holes separated at fixedintervals. These holes act as guides for the catheters. The TRUS probeis inserted into the rectum and placed so that the image corresponds tothe prostate base (the maximum depth). Two or three catheters areinserted into the tissue surrounding the prostate or in the periphery ofthe prostate to immobilize the gland. These catheters contain noradioactive seeds. This image serves as a spatial reference for allfurther images and seed positions within the prostate. Subsequently,catheters are inserted into the gland based on the pre-plan through thetemplate. The ultrasound probe is positioned each time so that thecatheter, and hence seeds, which are inserted into the prostate arevisible on the ultrasound image. If the placement of the catheter withinthe prostate is not according to the pre-plan, the catheter is thenwithdrawn and reinserted until the catheter is correctly placed. This isa time-consuming process; and it is very difficult to achieve optimalplacement. Invariably, the catheters deflect angularly as they areinserted, and their positions are difficult to determine bytwo-dimensional ultrasound. This is due to the fact that thevisualization process is a two-dimensional process while the actualimplant procedure is three-dimensional. Once all the seeds are in place,another series of two-dimensional images are obtained to quantify thefinal, resultant dose distribution delivered to the patient. In someinstances, a pair of orthogonal fluoroscopic images are also obtained todetermine the final seed placements. This procedure is usually performeda few weeks post implant.

[0010] These above described prior art systems suffer from inherentinaccuracy, the inability to correct the positioning of the radioactiveseeds without repeated withdrawal and reinsertion of seeds into theprostate and are not real time manipulations of the therapeutic medium.Further, the overall positioning of the template and patient may bedifferent during treatment compared to the assessment phase.Consequently, the catheter position and seed position may be at anundesired position relative to the presumed assessment phase location.

[0011] It is therefore an object of the invention to provide an improvedsystem and method for invasive treatment of the human body.

[0012] It is another object of the invention to provide a novel systemand method for real time and/or near real time, three-dimensionalvisualization of a human organ undergoing invasive treatment.

[0013] It is also an object of the present invention to provide a moreprecise and accurate implant placement for radiation therapy, thermaltherapy, and surgical ablation.

[0014] It is also an object of the invention to provide an improvedsystem and method for generating a three-dimensional image data set of ahuman organ for a treatment protocol using a real-time ultrasoundimaging system with spatial landmarks to relate the image data set topresent time, invasive treatment devices.

[0015] It is a further object of the invention to provide a novel systemand method for spatial registration of two-dimensional andthree-dimensional images of a human organ, such as the human prostate,with the actual location of the organ in the body.

[0016] It is an additional object of the invention to provide animproved method and system for three-dimensional virtual imaging of themale prostate gland and overlaid virtual imaging of devices beinginserted into the prostate for deposition of radioactive seeds forcancer therapy.

[0017] It is yet a further object of the invention to provide anautomated method and system for loading of radioactive therapeutictreatment seeds based on a clinical plan enabling rapid treatment basedon substantially real time pre-planning using rapid patient organevaluation.

[0018] These and other objects and advantages of the invention will bereadily apparent from the following description of the preferredembodiments thereof, taken in conjunction with the accompanying drawingsdescribed below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1A illustrates a block diagram of an embodiment of theinvention and FIG. 1B shows an alternate embodiment for athree-dimensional probe;

[0020]FIG. 2 illustrates an ultrasound guided implant system;

[0021]FIG. 3A illustrates patient setup for a radioactive implantprocedure; FIG. 3B illustrates an anatomical prostate phantom used fortesting and planning; and FIG. 3C illustrates in detail a probeholder/stepper assembly shown partly in FIG. 3A;

[0022]FIG. 4A illustrates a front schematic view of a brachytherapyphantom and FIG. 4B a side schematic view of the brachytherapy phantom;

[0023]FIG. 5A illustrates reconstruction of standard orthogonal imageplanes from a three-dimensional image stack and FIG. 5B thereconstruction of oblique image planes from a three-dimensional imagestack;

[0024]FIG. 6 illustrates the viewing geometry for a three-dimensionaltranslucent reconstruction of an image;

[0025]FIG. 7A illustrates translucent images of a human prostate forfour different viewing angles and FIG. 7B illustrates translucent imagesof a phantom organ for six different viewing angles;

[0026]FIG. 8 illustrates a time sequenced image of the prostate organ inFIG. 7A showing approach of a catheter containing a radioactive seed,deposition of the seed and withdrawal of the catheter leaving the seed;

[0027]FIG. 9 illustrates isodose distributions of radiation from asingle radioactive seed;

[0028]FIG. 10 illustrates a flow chart of software routine forprocessing imaging data for visualization;

[0029]FIG. 11 illustrates a virtual reality head mounted display;

[0030]FIG. 12 illustrates a flow diagram of software module operativeconnections;

[0031]FIG. 13A illustrates a perspective view of a stepper assembly withthe probe in position and FIG. 13B illustrates a perspective view of theprobe stepper along with a probe stabilization system; and

[0032]FIG. 14 illustrates a redundant monitoring and automatic loadingsystem for radioactive seeds and inert spacers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0033] A system 10 constructed in accordance with an example of theinvention is illustrated generally in FIG. 1. A three-dimensional probe12 accumulates image data from a treatment region or organ of a patient,image data is processed using a three-dimensional imaging card 14. Theprobe 12 preferably is an ultrasound device but can be any other rapidimaging technology, such as rapid CT or MR. A conventional personalcomputer 16 having a monitor can be used to operate on the image datafrom the imaging card 14 using conventional software and hardware toolsto be described in more detail hereinafter. Radioactive seeds 18 areprovided for insertion using any one of a variety of conventional meansfor inserting devices or articles into the human body, such as insertiondevices 19, which may be either needles or stiff catheters. Thethree-dimensional ultrasound probe 12, therefore, provides an imagesignal to the computer 16 and a virtual realty interface card 13 coupledto the imaging card 14 which enables a user to visualize a translucentimage of the patient organ and real time interaction of any one of avariety of treatment devices, such as the implant needles 19 or a Foleycatheter 20, and one of the seeds 18 within the organ. Computer softwarecan be utilized in a conventional manner to visualize thethree-dimensional imaging data in various formats (see Appendix anddiscussion hereinafter). The formats include orthogonal two dimensionalimages, oblique two-dimensional images, and translucentthree-dimensional rendering. All of these reconstructions can bedirectly displayed on the computer monitor; and three-dimensionaltranslucent, stereoscopic, rendering is also available in the VR(Virtual Realty) mode.

[0034] One of the preferred ultrasound probe 12 for example, is aconventional Kretz ultrasound imaging system manufactured by KretzCorporation, now available as Medison Combison 530 through MedisonAmerica Corporation, Pleasantown, Calif. This system and other suchconventional systems are readily available and can provide real timeultrasound image data. The Medison Combison ultrasound systemincorporates an endorectal probe which acquires multiple image planes inreal time and in certain embodiments the software (see Appendix)reconstructs the translucent three-dimensional volume. Another exampleis of a B&K Leopard ultrasound imaging system with endorectal imagingprobe (Boston, Mass.). Alternate systems include biplanartwo-dimensional imaging systems with the probe mounted in a steppermotor driven holder for rapid automatic acquisition of multiple imageplanes.

[0035] In a most preferred form of the invention, the system 10 includescomputer software for real-time image acquisition, image contouring,dose calculation and display software, dose volume histograms,three-dimensional dose contours, post-implant seed localization, and thepatient scheduling spreadsheet software. Attached is an Appendix ofcomputer software used to implement these functionalities. FIG. 12illustrates the operative connection between modules of the software.The system software enables a two-dimensional and three-dimensionalimage visualization for brachytherapy employing two-dimensionalultrasound imaging for use in radioactive seed implants of the prostate.The software for the brachytherapy seed implant and dose calculationsystem was developed on a Pentium-based processor with supportinggraphics and digitizing hardware. The software consists oftwo-dimensional and three-dimensional routines. The two-dimensionaltools consist of standard imaging tools largely available for CT and MRIapplications. These tools include displays of the imaging volume in anyof the three standard orthogonal planes (transverse, sagittal, andcoronal), in addition to the ability to display the imaging in anyarbitrary, oblique imaging plane. Standard image processing tools suchas real time window leveling, zoom and pan will be available. Thethree-dimensional tools consist of a three-dimensional rendering of theactual contour slices imaging data. Based upon volumetric patientstudies, the prostate volume can be displayed. The user has the optionof viewing one or a mixture of two-dimensional and three-dimensionalsurface views on the monitor.

[0036] Contouring tools are also available for the user to draw with themouse outlines, or contours, of any structure visible on the imagingplane. Each contour can be varied as to color, line thickness, and linepattern to aid in distinguishing between different contour sets.

[0037] Once a set of two-dimensional contours has been defined, eithermanually or automatically, on a number of different image slices theycan be reconstructed in real time in the three-dimensional translucentview (described in more detail hereinafter). This results in a surfacerendering of the volume bounded by the contours. The surface renderingcan be chosen to be transparent, solid, or invisible (not rendered atall).

[0038] Once a seed has been placed into treatment position (detailsconcerning seed implantation provided later), the user has the abilityto display the dose of one or a set of seeds. The dose as a function ofposition for a cylindrical¹²⁵ or ¹⁰³Pd seed of a given activity can bedetermined from a lookup table or calculated from an analytic formula.The dose field can be visualized as a set of isodose lines intwo-dimensions or isodose surface in three-dimensions. The process ofconstructing an isodose line or surface is defined by simply drawing apoint for each pixel/voxel which contains a certain specified dosevalue. For example, the user can specify that the 137 Gy, 120 Gy, 100Gy, and 60 Gy isodose lines be drawn on the two-dimensional slice foreach image plane, and the 137 Gy isodose surface shown on thethree-dimensional rendered mode. Again, similar to the contouredvolumes, the isodose surface can be reconstructed in any of the userselected modes defined for contoured volumes.

[0039] The features/capabilities of the system software functionalitiesinclude: complete patient database archive and dose plan “playback”;external image import capability; look-up tables for multiple seed kitsand template guides; multiple ultrasound imaging machine configurationcapability; image slice contouring using mouse, with edit capability;image cropping, image sizing, tiling, cascading; three-dimensionaldisplay of prostate, urethra, and other anatomies; rapid “on-line” dosecalculation in operating room/cysto suite during procedure; dose displaywith isodose lines, three-dimensional translucent, and ditheredisodoses; image export and printing (dose slices, contour slices, etc.);seed implant plan export and printing; dose volume histograms (withexport and printing); three-dimensional image support includingthree-dimensional image reconstruction from slices; three-dimensionaldisplay of isodose surfaces; image slice selection fromthree-dimensional image through any transverse plane; post-implantassessment including automatic seed localization; computer-controlledstepper; selection of manual (mouse entry), semi-automatic (buttonpush), or full automatic (computer-controlled stepper) ultrasound imagecollection.

[0040] For collecting ultrasound image data, the diagnostic transrectalultrasound probe 12 (see FIG. 2) is inserted into the patient's rectumto obtain real time volumetric images of the prostate for use during theimplant procedure. The diagnostic probe 12 is preferably a phased arrayprobe designed so that the array of transducers can rotate about theaxis of the array sweeping out a three-dimensional imaging volume. Asthe probe 12 rotates, images are captured and digitized by use of theimaging card 14 (see FIG. 1), so as to create a fixed number of imagesslices per rotation. An alternative method utilizes a transverseoriented phased array form of the endorectal probe 12 which is movedlongitudinally in an automated rapid sequence so as to create a seriesof transverse image slices automatically. Another embodiment of theprobe 12 can incorporate multiple transverse phased arrays (shown inphantom in FIG. 1B) arranged parallel to each other orthogonal to theaxis of an endorectal probe to produce multiple simultaneous imageslices (see, for example, FIGS. 5A and 5B). The three-dimensional imagedata will be represented as a three dimensional image raster.

[0041] The ultrasound probe 12 can be mounted into a probe holder 30(see FIGS. 3A and 3C) with FIG. 3B illustrating one example of anultrasound image from an anatomical prostate phantom employed to carryout testing and planning. The probe holder 30 includes a digital encoder42 for providing information regarding the position of all of thedesired ultrasound image planes in the prostate relative to each other.The image plane location will be automatically sent to the systemcomputer and “tagged” to the acquired ultrasound image for that position(FIG. 2). Thus, it will be possible to reproduce the longitudinal andlateral positions of the implant catheters for the ultrasound therapyapplicators and for the temperature probes.

[0042] A probe holder/stepper assembly 21 (see FIG. 1A and in particularFIG. 13) accommodates most ultrasound endorectal probes from variousmanufacturers. A “collett” 23 surrounds the probe 12 and is insertedinto the stepper/probe holder assembly 21. The stepper 21 is a digitaldevice with an automatic imaging link to the ultrasound machine and tothe remainder of the system 10. The stepper 21 has three digitallyencoded axes: main probe stage longitudinal axis 31, needle insertiontemplate longitudinal axis 33, and the rotational axis 35 of the imagingprobe itself. The stepper 21 automatically records the longitudinal(z-axis) position and sends that information to the computer 16.Whenever the user desires to acquire an image plane, the spatialposition of that image plane is automatically registered with thatimage. Thus, it requires less than a minute to digitally acquire anddocument all the image planes in a typical volume study. The stepper 21can be incrementally moved by the user with stepper knob 34 and thetemplate 25 can be stepped by template positioning control 37.

[0043] The holder/stepper assembly 21 can move the probe 12 in 2.5 mmincrements. A transrectal probe from B&K was used which operates at afrequency of 7.5 MHz and contains two sets of 128 transducer elementsforming both transverse and sagittal imaging assays. The imaging probe12 was moved via a knob on the side of the stepper 21 and its positionmeasured via a digitally interfaced optical position encoder. The probeholder/stepper 21 with transrectal probe 12 mounted is shown in FIG. 1.The real time multi-plane ultrasound probe 12 was modeled by obtainingsingle digitized transverse images at either 2.5 or 5 mm intervalsthrough the ultrasound prostate imaging phantom. The ultrasound prostatephantom is available from Computerized Imaging Reference Systems Inc.and contains a model of a prostate, urethra, and seminal vesiclesimmersed in a gel filled plastic box. The box has a cylindrical hole inthe base for the insertion and positioning of the transrectal probe anda perineal membrane for performing practice brachytherapy implants.FIGS. 4A and 4B display a schematic of the brachytherapy phantom. Oncethe static image slices have been digitized they were then inputted tothe software in a continuous cycle to model actual real time acquisitionof a full volume. Multiple sets of image slices can be obtained andrandomly cycled to more accurately simulate the actual three-dimensionalreal time ultrasound probe 12. The image slices are input to thesoftware transparently.

[0044] A probe stabilization system 27 (see FIG. 13B) is designed foruse with any standard probe holder/stepper 21, yet it is optimized foruse as part of the system 10. This stabilization system 27 attacheseasily and quickly to the cysto or operating room table using clamps 28,yet provides maximum flexibility during patient setup. The stabilizationsystem 27 provides for five degrees of freedom of motion, yet is robustand stable. The probe stabilization system 27 includes a stepper probestand control 28 which allows up and down movement. Further motioncontrol is provided by stabilizer control 29 which enables up and downmotion and left to right along rods 30 (horizontal) and rods 31(vertical). Gross motions are positively controlled in a stable manner.Fine motions are obtained with the same controls and are exactlyreproducible.

[0045] A variety of the templates 25 (see FIG. 1) for the needles 19 canbe used with the system 10. All of these implant templates aredisposable preferably. The system 10 can also accommodate use of otherstandard templates 25. The system software (see Appendix) can store theconfiguration of any number of the templates 25 for immediate recall.Each template 25 stored in the system 10 is spatially registered witheach ultrasound system configuration stored in the system software.

[0046] The system templates 25 provide assurance of sterility forpatient contact at a cost similar to that of sterilization of the usualstandard templates. The disposable system templates 25 are a fraction ofthe cost of standard reusable templates and provide greater safety.

[0047] There are several possible image processing cards which could beutilized; however, using current modalities each of the processing cardsis configured specifically for three-dimensional. The three-dimensionalimage raster is buffered; and thus, for example, if the two-dimensionalimages are 512×512 and there are sixteen image planes in the probe 12,and each pixel is a byte (256 gray scales), at least a 512×512×16byte=4.2 Mbyte image buffer in the card 14 is needed. Several commercialcards (for example, made by Coreco, Matrox and Integral Technologies)can be equipped with this amount of video RAM (VRAM), but the way thecard's hardware interacts with the computer's video and software driversdoes not utilize this data in three-dimensional. Current availablemethodologies enable augmenting the software and some hardware of thesecards so that they can act as a three-dimensional card. The processingand memory architecture preferably is designed to allow for simultaneousimage acquisition and processing. The digitizing card should alsopreferably have standard imaging tools, such as real time window andleveling, zoom and pan of the ultrasound images. Some existing cards(e.g., Matrox; Coreco) do provide standard imaging tools.

[0048] The three-dimensional image data arising from the ultrasoundprobe 12 is preferably buffered on the imaging card 14. Thethree-dimensional image is preferably represented as a series oftwo-dimensional images. This is referred to as the image stack orthree-dimensional image raster. The three-dimensional image raster isrepresented in memory as a linear array of bytes of length N×M×P where Nis the width of the two-dimensional image in pixels, M is the height atwo-dimensional image in pixels, and P is the number of two-dimensionalimages in the image stack.

[0049] In a preferred embodiment the user can include defined formats.Entire three-dimensional image stacks at specific times during theintraoperative session can be stored in the DICOM standard. The userwill have the ability to select a three-dimensional image volume forarchiving as part of the system software. These image stacks can then bereviewed in any of the various visualization modes (standard orthogonaltwo-dimensional views, oblique two-dimensional views, orthree-dimensional translucent views) as described above. In addition,the user will have the ability to store any of the two-dimensional viewsavailable at any time during the intraoperative session.

[0050] The computational platform can, for example, be any form ofcomputing means, such as the personal computer 16, which incorporates aPCI bus architecture. Currently, PCI bus is preferable over the ISA orEISA bus because the PCI bus is much faster. However, a generic systemwhich will be suitable for this applicable will be described. A 200 MHz(or greater speed) Pentium/Pentium-Pro computer supplied with 128 Mbytesof RAM and a 6.0 Gbyte hard disk should be sufficient RAM and diskmemory to run the software in a real-time fashion and to archive allpatient data. There should be sufficient RAM to facilitate host imageprocessing in parallel with onboard image processing for qualityassurance checks. A high resolution monitor capable of displaying atleast 1280×1024×64 bit resolutions is preferably used.

[0051] Based on currently available technology, the ultrasound imagesobtained from the ultrasound imaging system of the ultrasound probe 12can be of good diagnostic quality. When transforming this input imagedata into a three-dimensional representation, whether in thethree-dimensional perspective mode or the real time VR mode, theresultant volumes can, however, be noisy and hinder diagnostic andspatial accuracy. In order to improve the image quality, a number ofconventional hardware and software filters can be used which will filterthe incoming image data stored on the imaging card 14. Routines such asimage pixel averaging, smoothing, and interpolation can improve thethree-dimensional rendering of the imaging volume. These sets of filtersor routines are to be distinguished from the set of standard imagingtools running on the host CPU which are available within a conventionalimaging software package.

[0052] In the preferred embodiment, three of the perspective views arethe standard transverse, coronal and sagittal two-dimensional views.These three orthogonal views are taken from a user specified locationwithin the imaging space. For example, the user can request that thethree orthogonal views have their common centers at a spatial positionof (5.0 cm, 15.0, 25.0 cm) relative to the origin of the templatesystem. One also can select the reference point of either of the threeorthogonal views independently, that is the three views do not have tohave common center points. As mentioned hereinbefore, FIGS. 5A and 5Bshow examples of several example two-dimensional views from athree-dimensional ultrasound image volume. FIG. 6 shows a number ofpossible viewing directions, and FIG. 7 gives further examples oftranslucent three-dimensional viewing from different angles. Thethree-dimensional ultrasound image volume was obtained from actualultrasound images of a human prostate and of a prostate implant phantom.

[0053] On each of the views, one can define, draw and edit contoursusing conventional computer software, such as Microsoft Foundation Class(MFC) view files. Each contour can be given a unique name by the user,and then drawn by the user using the mouse of the computer 16. Allattributes of the contours such as name and color can, based onconventional imaging software, be user selectable. The user can alsoedit the contours by selecting functions, such as adding a point to acontour, deleting a point from a contour or deleting the entire contour.Once the contours are defined, the user has the option to render them inthree-dimensional or view in conventional two-dimensional mode on thethree-dimensional perspective mode or viewed in the VR mode. Again, allcontour three-dimensional attributes such as color, lighting, andshading are user controlled. The contours by default appear on thetwo-dimensional images, however, the user can control the individualcontour's two-dimensional and three-dimensional visibility.

[0054] In order to improve the ability to visualize the real time,three-dimensional information, the three-dimensional image raster can berendered as a real time, transparent, three-dimensional volume. Thistransparent volume can be viewed and displayed on the monitor of thecomputer 16 at any arbitrary viewing angle and is calculated usingconventional three-dimensional object reconstruction algorithms. Suchstandard algorithms can render a large imaging volume in fractions of asecond, even on present day computing platforms. The transparent natureof the reconstruction thus allows the user to “see” inside any objectswhich appear in the imaging volume. For example, if the prostate isimaged in the imaging volume, then it will be reconstructed as atransparent volume, in which other anatomical landmarks such as theurethra, tissue abnormalities or calcifications can be seen. Inaddition, if any other objects such as needles or catheters are insertedinto the prostate, and if they are visible in the ultrasound images,they will be seen as they enter the prostate (see FIG. 8 showingintroduction of the seed 18 with the catheter/needle 19). Since thevolumes are rendered as transparent solids, the needles 19 (and otherarticles) can thus easily be seen as they move inside the prostatevolume as well. Since the ultrasound images are obtained in real time,the three-dimensional perspective reconstruction is also rendered inreal time. The preferred algorithm for the perspective three-dimensionalreconstruction is the known Bresenham ray-trace algorithm.

[0055] As described above, in the routine process of brachytherapyplanning, the patient undergoes an initial volumetric ultrasound scanusing the probe 12. This scan is done before the radiation therapyplanning or the actual implant. During the radiation therapy planning,the ideal positions of the radioactive seeds 18 (see FIG. 1) within theprostate are determined. This ideal seed distribution is optimized todeliver a dose distribution within the prostate that will deliver allthe radiation dose to the target volume only, while sparing thesurrounding healthy tissues such as the rectum and bladder. The optimalpositions of the seeds 18 and the optimal position of the needles 19 arerecorded for later use in the operating room when the needles 19 areloaded into the patient. The seeds 18 are then loaded into the needles19, and the physician then attempts to place the needles 19 inside theprostate using a template 25 according to the treatment dose planpositions (again, see example in FIG. 8).

[0056] In the most preferred embodiment the seeds 18 are loaded throughthe needles 19. A selection of different types of the seeds 18(different levels of radioactivity) can be loaded through passageways,P, shown in FIG. 14. Optical sensors 90 and 91 are redundantly disposedadjacent each of the passageways P with an associated microprocessor 93and 97 monitoring the number of the seeds 18 being instilled through theneedle 19. Radiation sensors 96 and 98 monitor the radiation activity ofthe seeds 18 being loaded into the needle 19. Spacers 100 are alsoinstilled into the needle 19 for separating the seeds 18 to achieve thedesired level of radiation activity and radiation contours. Opticalsensors 92 sense, redundantly as for the seeds 18, the passage of thespacers 100.

[0057] In a most preferred form of the invention, an automaticseed/needle loading method is implemented automatically loading implantneedles 19 with the radiation seeds 18 and spacers 29 based upon apre-plan (dose plan) determined in the operating room (OR). This methodaccommodates the spacers 29 and separate leaded-acrylic see-through“bins” for the seeds 18 of two different activity levels. Thus, theneedles 19 can be auto-loaded based upon optimal dose plans requiringseeds of different activity levels. The automatic seed/needle loadingmethod and system interfaces directly to the computer 16 and reads thedose plan information using the software of the Appendix. A display onthe auto-loader then displays to the operator each needle number,template coordinate location, and status of needle loading. Each of theneedles 19 are attached one at a time to the auto-loader assembly with astandard luer lock. The auto-loader has a sensor at the needleattachment point which detects if the needle 19 is attached for loading.Each of the needles 19 are then loaded in accordance with the pre-plan.

[0058] The automatic seed/needle loading method and system is thereforecompletely double-redundant, as mentioned hereinbefore. It incorporatesthe use of two totally independent microprocessors 93 and 94 whichconstantly check each other. Both the microprocessors 93 and 94 are alsoin communication with the system computer 16. The seeds 18 and thespacers 29 are optically counted independently. Needle loading isoptically checked for total number of loaded items and, further, aradiation detector array scans each needles 19 to confirm that theseed/spacer loading radiation pattern matches the pre-plan. Thisautomatic method and system will do so in the operating room in minimaltime, without the risk of human error in the loading of needles. Theseed loading method will include a pair of redundant 8051microcontrollers (the microprocessors 93 and 94) which will beinterfaced to the dose-planning and implant system computer 16 via aserial port. This interface will read the dose pre-plan information fromthe computer 16, without the need for paper printouts and manualloading. That information will be transferred to a controller whichcontrols the loading of each needle 19. The requirements and designcriteria for the automatic seed-needle loading method and system aredescribed as follows: self-contained and capable of loading seeds andspacers; system will protect operator of system from radiation; dualredundant counting of seeds and spacers; dual redundant radiationdetectors for measuring radiation from active seeds versus spacers; dualredundant measurement of radiation seed positions in needles; systemcheck for failure of either or both redundant counting and measurementsystems; alarm to both operator and to dose-planning and implantcomputer system in the event of error; ongoing account of seed andspacer inventory; tracks needle loading configuration and displays tooperator the designated template grid hole coordinates for each needleloaded; sterilized cassettes for holding seeds and spacers, plussterilizable needle connector; includes one cassette for seeds and onecassette for spacers; dispenses one seed and one spacer at a time, andverifies optically and by radiation detector; system displays needlenumber and template grid location during loading procedure; automaticacquisition of needle loading plan from main system computer; serialinterface with handshake protocol and verification; self-contained(mechanical, power, logic, microcontrollers); operates only if connectedto main system computer.

[0059] A convenient storage system for the needles 18 can be loaded bythe automatic seed/needle loading method system. The face of this unithas a hole grid pattern which matches the implant template 25. Loadedneedles may be inserted into this unit until they are used. The entireunit is shielded for radiation leakage minimization. The template-likeface of the unit is available in both a reusable, sterilizable versionand disposable versions which match all standard implant template faces.Faces of the unit detach easily and quickly for sterilization ordisposal.

[0060] The dose as a function of position for a cylindrical ¹²⁵I seed ofa given activity can be determined from a lookup table or calculatedfrom a conventional analytic formula. The dose field can be visualizedas a set of isodose lines in two-dimensional or isodose surface inthree-dimensional. The dose computation routine is based upon the TG43standard adopted by the AAPM (American Association of Physicists inMedicine) entitled “Dosimetry of Interstitial Brachytherapy Sources”:Recommendations of the AAPM Radiation Therapy Committee Task Group No.43 which specifies the dose model and the data used in the dosecalculation. This particular implementation runs extremely fast on aconventional 233 MHz PC, computing the dose for a single seed in lessthan 0.5 seconds. The total three-dimensional dose distribution withinthe prostate for a 100 seed implant requires only 50 seconds, or lessthan one minute total computation time. Thus, this can be done “on line”in the operating room.

[0061] In the two-dimensional, three-dimensional perspective, or thereal time VR modes, the user has the ability to view the optimized seeds18 and the needles 19 in the same volume as the real time ultrasounddata. This allows the physician to see exactly where the needles 19should go and hence make adjustments to position the needles 19optimally. The pre-planned, optimal positioned needles 19 and the seeds18 can be rendered again as a transparent solid, the color of which isuser selectable. As the real needles 19 are inserted into the prostate,their positions relative to the ideal needle placements based on thedose plan can be monitored in real time. Any deviation of the positionof a given needles 19 can be quickly and accurately readjusted so as tofollow the path of the ideal needles 19. As the different needles 19 areplaced at different positions inside the prostate, the viewing angle canbe adjusted to facilitate viewing of the needle or catheter placement.FIGS. 5A and 5B displays perspective three-dimensional views and thethree orthogonal reconstructions of the image data along with thepre-planned catheter positions. The pre-planned needles 19 can also beviewed in the VR mode as virtual objects overlaid onto the imagingvolume.

[0062] A flowchart description of the translucent volume visualizationmethodology is shown in FIG. 10. The input image volume is described bythe vectors i, j, k of appropriate magnitude for the volume. The viewingangle parameters are the angles θ, Ø described on FIG. 6 and FIG. 10.The rotation matrix, R, is calculated using the formulae given in theflowchart of FIG. 10. The entire imaging volume is calculated bymultiplying the rotation matrices in the x, y, z directions by therespective vectors i, j and k describing the incremental portions alongthe x, y, z directions. Thus, the multiplying vector is (i-i_(o),j-j_(o), k-k_(o)) where i_(o), j_(o), k_(o) are the starting pointsalong x, y and z axes and the volume is determined by summing thecomponent contributions shown in FIG. 10. The three-dimensionaltranslucent image is then created by computing the translucenttwo-dimensional image over the entire image volume and summing thez-pixels.

[0063] A virtual reality interface system can be composed of aconventional head mounted display (HMD) 50 shown in FIG. 11 and a 6D(x,y,z, roll, pitch, yaw) tracking system. The HMD 50 consists of twocolor monitors which mount to a head set in the position directly infront of the eyes. The HMD 50 is based on the principal that whatever isdisplayed on each monitor is directly incident on the retina for eacheye, and hence true three-dimensional images can be created by renderingobjects as three-dimensional perspective images for each eye. Given thedistance between the eyes (the interocular distance which isapproximately 80 mm) and the distance and spherical angles of thedistance of the center line between the eyes from the coordinate origin,the two-dimensional images which appear in each of the two monitors canbe determined exactly as described above. This results in a truethree-dimensional image as perceived by the user. Therefore, as the usermoves his or her head or moves around the room, the distance from theorigin and the spherical angles also change. This motion of the user oruser's head can be obtained from the VR tracking system. Given thesespatial parameters, the images which are reconstructed in the two eyemonitors can be updated in real time, giving the user the illusion ofthe object really existing in three-dimensional space. The userliterally has the ability to walk around the object, viewing it inthree-dimensional space.

[0064] Instead of reconstructing computer generated geometric objects asis usually the case in VR, the transparent, three-dimensionalreconstruction of the real time imaging data will preferably bereconstructed. Hence as the physician walks around the patientundergoing the implant, the physician will see the three-dimensionalultrasound volume mapped inside the patient's pelvis, spatiallycorrelated to the position of the patient's real prostate (or otherorgan) and anatomy. The physician can “see” inside the patient to theextent of what is visible in the ultrasound imaging volume. Since theultrasound probe 12 is locked down to the template, which is thensecured to the floor, the exact positions of all voxels in theultrasound imaging volume are known exactly relative to the template,and hence relative to the room.

[0065] As the needles 19 are inserted into the patient, they will appearin the image volume and hence are reconstructed in the VRreconstruction. All of this occurs in real time so that the physicianalso can see the needles 19 enter the prostate in real time. Asmentioned above, if the pre-planned, optimized needles 19 are displayed,the physician can then see the position of the actual needles 19 as theyare being inserted relative to the optimal placement. Hence, thephysician has the ability to adjust the needles 19 to correspond totheir optimal positions. In addition, since the needles 19 areautomatically extracted, the computer software has the ability tocalculate and render the three-dimensional dose distribution in realtime as the needles 19 are being inserted.

[0066] As an example, a currently available, a fast and inexpensive HMDis made by Virtual-IO Corporation (Mountain View, Calif.). The HMD isfull color with two 0.70 LCD displays with a resolution of 180,000pixels per LCD panel. The video input is NTSC with field sequentialformat. The LCD panels are semitransparent, allowing the real outsideworld to be included in the virtual reconstruction. The field of view is30° for each eye. A six degree of freedom (6 DOF) tracking system canalso be attached to the HMD. The 6 DOF tracking system allows for thedetermination of the spatial position of the user's head and the yaw,pitch, and roll of the head. The conventional head set weighs only 8ounces and comes with stereo sound. Stereo sound is an extremelyvaluable technology in the operating room. With this capability, thephysician has the ability to monitor the patient's heart rate andrespiration rate while performing the implant. Hence any fluctuation inthe patient's vital signs can be instantly accessed and acted thereon ifnecessary.

[0067] The radioactive seeds 18 are made of high density material suchas stainless steel, and hence have a very bright response in theultrasound images. Therefore, automatic seed detection in the ultrasoundimages can readily be accomplished, for example, by a simplethresholding algorithm along with the requirement that the resultantobjects which are removed by threshold have a certain maximum sizedetermined by the actual size of the seeds.

[0068] Near-real-time visualization will provide immediate feedback tothe physician during the implant process itself. There is a clear needfor the visualization being available during the implant process. Thenearly real time visualization is of great importance to the effectiveuse of a translucent overlay of the ideal seed pre-plan (from thetherapy planning process) in the three-dimensional volume. The physiciancan “see” in nearly real time the relationship of the needles and seedsbeing implanted to the ideal pre-plan locations and quickly accommodateredirection required prior to leaving the radiation seeds. Further, theneed for this in three-dimensional representation is very important toovercome the greatest fundamental limitation in brachytherapy, which isknowing at the same time both the lateral placement and longitudinalplacement of needles and seeds relative to the target volume andpre-plan. This is a three-dimensional problem which has up until nowbeen addressed in two-dimensional in a stepwise fashion without theability to “see” the exact location of where you are in the target. Thisreal time three-dimensional visualization also would speed the implantprocess in the case of brachytherapy as well as make it more accurate.It would also speed other minimally invasive surgical procedures andlocalized tissue ablation procedures (for example, cryosurgery orlocalized selected ablation of diseased liver tissue or local removal ofbreast tissue). These procedures could be accomplished with real timevisualization inside the tissue being treated with greater accuracy inshorter time. This aspect would reduce operating room time and costs tothe patient and health care system.

[0069] While preferred embodiments of the inventions have been shown anddescribed, it will be clear to those skilled in the art that variouschanges and modifications can be made without departing from theinvention in its broader aspects as set forth in the claims providedhereinafter.

What is claimed is:
 1. An apparatus for imaging and treatment of anorgan of the body of a patient, comprising: means for providing imagedata from a treatment region of the patient's body; means for developinga therapy plan for treatment of the organ of the patient; and means forautomatically loading radioactive seeds and spacers through needlesinserted into the organ of the patient to achieve the therapy plan.